1. Field of the Invention
This invention relates in general to integrated circuits and in particular to integrated circuits with differently strained channels for transistors of different conductivity types.
2. Description of the Related Art
The strain of a channel of a transistor affects the carrier mobility of the transistor. Strain may be induced either intentionally or unintentionally during the manufacture. A particular strain differently affects the electron mobility of N-channel transistors and the hole mobility of P-channel transistors. A particular strain may be more desirable for the operating speed of an N-channel transistor and less desirable for the operating speed of a P-channel transistor. For example, a more tensile strain of a channel region may provide for an increase in electron mobility and a decrease in hole mobility.
What is desired is an integrated circuit with improved operating speeds for both N-channel transistors and P-channel transistors.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The Figures are not necessarily drawn to scale.